The measurement of surface contours of an object using optical measurements of light reflected from a target surface of the object is generally known. For instance, the use of two-phased patterns for reconstructing a 3D profile of an object is disclosed in U.S. Pat. No. 6,049,384.
As shown in FIG. 1a, the apparatus 100 disclosed in U.S. Pat. No. 6,049,384 comprises: i) first and second lighting devices 102, 104; ii) a timing circuit 106 coupled to the first and second lighting devices 102, 104; iii) a reticle 108 having alternating areas of metallized and transparent strips; iv) a detector 112; and v) a processor 114. When the timing circuit 106 activates only the first lighting device 102, light is projected from the first lighting device 102 onto the reticle 108 and a target surface 110 of an object along a single line of travel as shown. In particular, the transparent strips of the reticle 108 allow light to pass through to reach the target surface 110 while the metallized strips reflect light away from the target surface 110. Consequently, a pattern comprising a plurality of strips alternating between different light intensities is formed on the target surface 110, as shown in FIG. 1b. 
On the other hand, when the timing circuit 106 activates only the second lighting device 104, light projected from the second lighting device 104 onto the reticle 108 and the target object 110 along different lines of travel as shown. In particular, the metallized strips of the reticle 108 reflect light towards the target surface 110 while the transparent strips of the reticle 108 allow light to pass through in a direction away from the target surface 110. Thus, a pattern comprising a plurality of strips alternating between different light intensities is also formed on the surface of the target object 110, as shown in FIG. 1c. 
The detector 112, arranged at a triangulation angle ∅ relative to a focal plane of light projection by the lighting devices 102, 104, is adapted to capture respective images of the patterns as formed on the surface of the target surface 110 upon a sequential projection of light by each of the first and second lighting devices 102, 104. Based on the images as imaged by the detector 112, the processor 114 accordingly produces a 3D image of the surface of the target object 110.
It should be noted that the respective patterns of FIGS. 1 b and 1 c are exactly aligned but 180° out of phase. In order to achieve these pattern requirements, the position of the lighting devices 102, 104 must conform to a certain relationship. In other words, a positional adjustment of any of the lighting devices 102, 104 necessitates a corresponding positional adjustment of the other of the lighting devices 102, 104. Moreover, a positional adjustment of the reticle 108 also necessitates a corresponding positional adjustment of both the lighting devices 102, 104. Such requirements undesirably complicate the assembling of the apparatus 100. Furthermore, the angle of the reticle 108 is constrained by the angle of light projection from the lighting devices 102, 104 and, accordingly, the focal plane of light projection may not align with the object plane of the target surface 110. This may undesirably cause uneven periods and fringe amplitudes of the patterns that are formed on the target surface 110.
It is therefore an object of the present invention to seek to ameliorate the above limitations of the conventional apparatus 100, and to provide the general public with a useful choice.